Quantum Entanglement of Localized Excited States at Finite Temperature

TL;DR

This paper investigates how localized excitations affect entanglement entropy in two-dimensional conformal field theories at finite temperature, revealing temperature-dependent growth patterns and late-time saturation behaviors.

Contribution

It provides a comparative analysis of entanglement dynamics in free and holographic CFTs at finite temperature, including field theoretic and holographic calculations.

Findings

Finite temperature reduces entanglement growth in free CFTs.

Holographic CFTs show late-time entanglement saturation.

Mutual information in thermofield double states offers physical insights.

Abstract

In this work we study the time evolutions of (Renyi) entanglement entropy of locally excited states in two dimensional conformal field theories (CFTs) at finite temperature. We consider excited states created by acting with local operators on thermal states and give both field theoretic and holographic calculations. In free field CFTs, we find that the growth of Renyi entanglement entropy at finite temperature is reduced compared to the zero temperature result by a small quantity proportional to the width of the localized excitations. On the other hand, in finite temperature CFTs with classical gravity duals, we find that the entanglement entropy approaches a characteristic value at late time. This behaviour does not occur at zero temperature. We also study the mutual information between the two CFTs in the thermofield double (TFD) formulation and give physical interpretations of our results.